Films produced in foreign countries are sometimes dubbed into the mother tongue or added with the native language subtitles before they are released. Bilingual TV broadcasting systems have been developed, in which the user can select the desired language at his or her TV set.
The user can select either of the two languages but cannot select any other language.
The market of systems using recording mediums (films, disks, magnetic tape, etc.) has expanded worldwide. Demand has therefore grown for systems capable of reproducing recorded information be in more than one, or even two, languages.